Abstract
I report on the progress of two new muon anomalous magnetic moment experiments, which are in advanced design and construction phases. The goal of Fermilab E989 is to reduce the experimental uncertainty of $a_\mu$ from Brookhaven E821 by a factor of 4; that is, $\delta a_\mu \sim 16 \times 10^{-11}$, a relative uncertainty of 140~ppb. The method follows the same magic-momentum storage ring concept used at BNL, and pioneered previously at CERN, but muon beam preparation, storage ring internal hardware, field measuring equipment, and detector and electronics systems are all new or upgraded significantly. In contrast, J-PARC E34 will employ a novel approach based on injection of an ultra-cold, low-energy, muon beam injected into a small, but highly uniform magnet. Only a small magnetic focusing field is needed to maintain storage, which distinguishes it from CERN, BNL and Fermilab. E34 aims to roughly match the previous BNL precision in their Phase~1 installation.
Highlights
At this Workshop, more than 25 presentations were devoted to topics centered on the muon anomalous magnetic moment, aμ ≡ (g − 2)/2
These included a discussion of the two new measurement campaigns – as reported in this paper – and the theoretical issues related to both the Standard Model prediction and various new-physics speculations
I will focus mainly on the Fermilab E989 experiment, which is in a mature construction state
Summary
At this Workshop, more than 25 presentations were devoted to topics centered on the muon anomalous magnetic moment, aμ ≡ (g − 2)/2. These included a discussion of the two new measurement campaigns – as reported in this paper – and the theoretical issues related to both the Standard Model prediction and various new-physics speculations. Efforts to evaluate the SM are considered These topics received extensive scrutiny at this Workshop. If this range for ΔaNμ ew is confirmed at a greater significance, the positive sign and relatively large magnitude – several times greater than the electroweak contribution – will provide important clues to the physics it is trying to reveal. The key phrase above is, “at a greater significance.” Let’s first focus on the combined experimental and theoretical uncertainty of 80 × 10−11 and investigate what contributes to this value and how the combined error might be reduced in the future
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